There is known, as a rotation sensor having a pair of rotors and a stator containing an exciting coil and detecting a running torque between two shafts rotating relative to each other, for example, one which is utilized for smooth electronic control of a steering device. The sensor detects a running torque in an automotive handle shaft having two rotating shafts rotating relative to each other and connected to each other through a torsion bar (see, for example, Examined Japanese Patent Publication(Kokoku) No. Hei 7-21433). 
Here, in the conventional rotation sensor described above, the rotors are fixed beforehand to the rotating shafts respectively, and a rotation guide such as a bearing is interposed between the stator and each rotating shaft to achieve alignment of the rotating shafts of these two rotors with the central axis of the exciting coil in the stator.
However, according to the above constitution, the rotation sensor must be manufactured or assembled integrally with two rotating shafts rotating relative to each other to impose design limitation on a target to which the rotation sensor is attached, e.g., a steering device. In addition, the rotation sensor generally needs adjustment of sensitivity and output range, and when it is integrated into the rotating shafts, such adjustments are carried out after completion of assembly. Therefore, the resulting rotation sensor involves problems that the adjusting mechanisms are enlarged and complicated due to upsizing by integration into the rotating shafts.